A carrier may protect the semiconductor substrates, for example, from foreign matter in the air and chemical contamination, by holding the substrates in a sealed space. The sealed carrier, such as a FOUP (front opening unified pod) or a SMIF (standard mechanical interface) pod, is generally formed from a high-performance plastic material. However, humidity and oxygen content tend to increase with time, due to the moisture permeability of plastic materials, or due to the oxygen molecular diffusion, since for reasons of safety and handling, carriers are generally not constructed to be hermetically sealed.
In addition, vaporized organic solvent from substrate coatings, such as a photoresist substrate, may adhere to the internal wall of the carrier. Thus the atmosphere inside the carrier may be contaminated with organic compounds.
As a measure against humidity, oxygen and organic contaminants in a carrier, dry air or nitrogen may be introduced to the sealed carrier to purge and replace the atmosphere inside the carrier. High purge flow, e.g., up to 150 l/min flow, together with larger volume containers, e.g., for 450 mm substrates, may require a significant amount of consumable purge gas.
Thus there is a need for a container purging system and method to reduce the consumption of purge gas, while maintain a cleanliness storage environment for the semiconductor substrates.